10 things we didn't know about lighthouses

Henry Hanks and Katie Hawkins-Gaar, CNN • Updated 11th December 2017

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(CNN) — In honor of National Lighthouse Day, we invited you to share your best lighthouse photos with CNN iReport. As dozens of images started pouring in, we were reminded of a near-universal fact: People love lighthouses. The beacons of light are popular destinations across the world.

6. The world's oldest existing lighthouse is considered to be Tower of Hercules, a UNESCO World Heritage Site that marks the entrance of Spain's La Coruña harbor. The lighthouse, which was erected in the first century, is still operational.

7. The most expensive lighthouse built in America is St. George Reef, near Crescent City, California. It took 10 years to construct and cost $715,000.

8. Lighthouse keeping was one of the first U.S. government jobs available to women, going back to the 19th century.

9. Despite advances in technology, lighthouses are still considered aids to navigation by the U.S. Coast Guard.

10. Towers are given different colors and patterns -- diamonds, spirals and stripes, for example -- to distinguish them from each other.